Artifacts
as time markers

Soda
bottles recovered at Manassas National Battlefield Park can be
dated by designs embossed on the glass. (Mia Parsons)

Changing
technology has created a vast number
of artifacts that mark specific time periods in archeology. These
are called diagnostic artifacts because they allow archeologists to
pinpoint relatively specific time periods during which they were produced.
Archeologists studying prehistoric cultures use stone and bone tools
to understand technological changes and assign approximate dates to
sites. Historical archeologists have found increasingly detailed ways
to partition time on their sites. For example, archeologists can date
a glass bottle based on attributes that demonstrate how it was made.
A hand-blown wine bottle made of thick, olive green glass is much
earlier than a machine-molded medicine bottle made of clear glass
and embossed with the manufacturer's name and logo. Documented patterns
in manufacturing technology allow archeologists to determine the absolute
dates for most glass bottles, ceramics, nails and other artifacts
found at historic sites. The most common diagnostic artifacts are
described below.